Synthesis and characterization of monomeric siloxo palladium(II) complexes: crystal structure of [Pd(tmeda)(C6F5)(OSiPh3)]

Mononuclear palladium-hydroxo complexes of the type [Pd(N-N)(C₆F₅)(OH)] [(N-N)=2,2^′-bipyridine (bipy), 4,4^′-dimethyl-2,2^′-bipyridine (Me₂bipy), or N,N,N^′,N^′-tetramethylethylenediamine (tmeda)] react with silanols HOSiR₃ in toluene giving the corresponding siloxo complexes [Pd(N-N)(C₆F₅)(OSiR₃)]. The X-ray crystal structure of [Pd(tmeda)(C₆F₅)(OSiPh₃)] has been determined. In one of the two molecules in the asymmetric unit there is an intramolecular interaction by phenyl-pentafluorophenyl π-stacking.     

Inorganic-Organic Hybrid Materials: Synthesis and X-Ray Structure of N,N′-Dimethylimidazolium Salts [(Me2Im)2][Cd2(SCN)6] and N,N′-Dicyclohexylimidazolium [(Cy2Im)2][Cd2(SCN)6]·C3H6O

Two novel N,N′-dialkylimidazolium thiocyanate-cadmium complexes [(R₂Im)₂][Cd₂(SCN)₆] for R=Me (3), and cyclohexyl (4) have been synthesized and characterized by single-crystal X-ray diffraction. Compound 3 crystallizes in the monoclinic unit cell dimensions of 17.468(3), 7.7273(12), 10.6750(16) Å, 104.833(2)°, and space group C2 with two [(Me₂Im)₂] [Cd₂(SCN)₆] per unit cell. The two cadmium atoms in 3 are octahedrally coordinated in 4N2S and 2N4S coordination environment, and linking into one-dimensional zigzag chains. Compound 4 belongs to the monoclinic space group Cc with unit cell of dimensions 13.3049(12), 17.5550(16), 20.8012(19) Å, 101.494(2)°, and four [(Cy₂Im)₂][Cd₂(SCN)₆]·C₃H₆O per unit cell. The cadmium atoms in 4 are all 3N3S hexa-coordinated with six bridging SCN⁻ ions in an fac configuration and form infinite zigzag polymeric chains. The infinite chains in 3 form an approximate hexagonal array, making triangular channels which are occupied by N,N′-dimethylimidazolium ions, whereas the chains in 4 form layered structure, and the layers are stacked perpendicularly with respect to the orientation of the infinite anionic chains alternatively. N,N′-dicyclohexylimidazolium cations and solvent molecules fill in between layers.     

Reactivity of 2,3-bis(2-pyridyl)pyrazine with [Re2(CO)8(CH3CN)2]: Molecular structures of [Re2(CO)8(C14H10N4)] and [Re2(CO)8(C14H10N4)Re2(CO)8]

The reaction of the labile compound [Re₂(CO)₈(CH₃CN)₂] with 2,3-bis(2-pyridyl)pyrazine in dichloromethane solution at reflux temperature afforded the structural dirhenium isomers [Re₂(CO)₈(C₁₄H₁₀N₄)] (1 and 2), and the complex [Re₂(CO)₈(C₁₄H₁₀N₄)Re₂(CO)₈] (3). In 1, the ligand is σ,σ′-N,N′-coordinated to a Re(CO)₃ fragment through pyridine and pyrazine to form a five-membered chelate ring. A seven-membered ring is obtained for isomer 2 by N-coordination of the 2-pyridyl groups while the pyrazine ring remains uncoordinated. For 2, isomers 2a and 2b are found in a dynamic equilibrium ratio [2a]/[2b]  =  7 in solution, detected by ¹H NMR (−50 °C, CD₃COCD₃), coalescence being observed above room temperature. The ligand in 3 behaves as an 8e-donor bridge bonding two Re(CO)₃ fragments through two (σ,σ′-N,N′) interactions. When the reaction was carried out in refluxing tetrahydrofuran, complex [Re₂(CO)₆(C₁₄H₁₀N₄)₂] (4) was obtained in addition to compounds 1-3. The dinuclear rhenium derivative 4 contains two units of the organic ligand σ,σ′-N,N′-coordinated in a chelate form to each rhenium core. The X-ray crystal structures for 1 and 3 are reported.     

Radical scavenging efficiency of different fullerenes C60-C70 and fullerene soot

This investigation was undertaken to determine the antioxidant activity of a range of fullerenes C₆₀ and C₇₀ in order to rank them according to their comparative efficiency. The model reaction of initiated (2,2′- azobisisobutyronitrile, AIBN) cumene oxidation was used to determine rate constants for addition of radicals to fullerenes. Measurements of oxidation rates in the presence of different fullerenes showed that the antioxidant activity as well as the mechanism and mode of inhibition were different for fullerenes C₆₀ and C₇₀ and fullerene soot. All fullerenes - C₆₀ of gold grade, C₆₀/C₇₀ (93/7, mix 1), C₆₀/C₇₀ (80 ± 5/20 ± 5, mix 2) and C₇₀ operated as alkyl radical acceptora, whereas fullerene soot surprisingly retarded the model reaction by a dual mode similar to that for the fullerenes and with an induction period like many of the sterically hindered phenolic and amine antioxidants. For the C₆₀ and C₇₀ the oxidation rates were found to depend linearly on the reciprocal square root of the concentration over a sufficiently wide range thereby fitting the mechanism for the addition of cumylalkyl radicals to the fullerene core. This is consistent with literature data on the more ready and rapid addition of alkyl and alkoxy radicals to the fullerenes compared with peroxy radicals. Rate constants for the addition of cumyl radicals to the fullerenes were determined to be k_(333K) = (1.9 ± 0.2) × 10⁸ (C₆₀); (2.3 ± 0.2) × 10⁸ (C₆₀/C₇₀, mix 1); (2.7 ± 0.2) × 10⁸ (C₆₀/C₇₀, mix 2); (3.0 ± 0.3) × 10⁸ (C₇₀), M⁻¹ s⁻¹. The increasing C₇₀ constituent in the fullerenes leads to a corresponding increase in the rate constant.The fullerene soot inhibits the model reaction according to the mechanism of trapping of peroxy radicals; the oxidation proceeds with a pronounced induction period and kinetic curves are linear in semi-logarithmic coordinates.For the first time the effective concentration of inhibiting centres and inhibition rate constants for the fullerene soot have been determined to be fn[C₆₀−soot] = (2.0 ± 0.1) × 10⁻⁴ mol g⁻¹ and k_inh = (6.5 ± 1.5) × 10³ M⁻¹ s⁻¹ respectively.The kinetic data obtained specify the level of antioxidant activity for the commercial fullerenes and scope for their rational use in different composites. The results may be helpful for designing an optimal profile of composites containing fullerenes.     

Reaction of C60 with KMnF4 : Isolation and characterization of a new isomer of C60F8 and re-evaluation of the structures of C60F7(CF3) and the known isomer of C60F8

The volatile fluorofullerene products of high-temperature reactions of C₆₀ with the ternary manganese(III, IV) fluorides KMnF₄, KMnF₅, A₂MnF₆ (A⁺ = Li⁺, K⁺, Cs⁺), and K₃MnF₆ were monitored as a function of reaction temperature, reaction time, and stoichiometric ratio by in situ Knudsen-cell mass spectrometry. When combined with fluorofullerene product ratios from larger-scale (bulk) screening reactions with the same reagents, an optimized set of conditions was found that yielded the greatest amount of C₆₀F₈ (KMnF₄/C₆₀ mol ratio 28-30, 470 °C, 4-5 h). Two isomers of C₆₀F₈ were purified by HPLC, one of which has not been previously reported. Quantum chemical calculations at the DFT level combined with 1D and 2D ¹⁹F NMR, FTIR, and FT-Raman spectroscopy indicate that the C₆₀F₈ isomer previously reported to be 1,2,3,8,9,12,15,16-C₆₀F₈ is actually 1,2,3,6,9,12,15,18-C₆₀F₈, making it the first high-temperature fluorofullerene with non-contiguous fluorine atoms. The new isomer, which was found to be 1,2,7,8,9,12,13,14-C₆₀F₈, is predicted to be 5.5 kJ mol⁻¹ more stable than 1,2,3,6,9,12,15,18-C₆₀F₈ at the DFT level. In addition, new DFT calculations and spectroscopic data indicate that the compound previously isolated from the high-temperature reaction of C₆₀ and K₂PtF₆ and reported to be 16-CF₃-1,2,3,8,9,12,15-C₆₀F₇ is actually 18-CF₃-1,2,3,6,8,12,15-C₆₀F₇.     

High-temperature and photochemical syntheses of C60 and C70 fullerene derivatives with linear perfluoroalkyl chains

New experimental results on perfluoroalkylation of C₆₀ and C₇₀ with the use of R_fI (R_f = CF₃, C₂F₅, n-C₃F₇, n-C₄F₉, and n-C₆F₁₃), along with a critical overview of the existing synthetic methods, are presented. For the selected new fullerene (R_f)_n compounds we report spectroscopic, electrochemical and structural data, including improved crystallographic data for the isomers of C₇₀(C₂F₅)₁₀ and C₆₀(C₂F₅)₁₀, and the first X-ray structural data for the dodecasubstituted perfluoethylated C₇₀ fullerene, C₇₀(C₂F₅)₁₂, which possesses unprecedented addition pattern.     

H2O@open-cage fullerene C60: control of the encapsulation property and the first mass spectroscopic identification

A novel open-cage C₆₀ derivative (a 19-membered ring orifice), prepared by the sequential cage scission reactions of the ketolactam derivative of C₆₀ with o-phenylenediamine, allows the encapsulation of one water molecule. The resulting endohedral water complexes were confirmed for the first time by mass spectroscopy. The efficiency of the encapsulation was affected by the substituent on the nitrogen atom.     

Synthesis and molecular structures of heptafluoroisopropylated fullerenes: C60(i-C3F7)8, C60(i-C3F7)6, and C60(CF3)2(i-C3F7)2

One isomer of C₆₀(i-C₃F₇)₈, three isomers of C₆₀(i-C₃F₇)₆, and the first mixed perfluoroalkylated fullerene, C₆₀(CF₃)₂(i-C₃F₇)₂, have been isolated by HPLC from a mixture prepared by reaction of C₆₀ with heptafluoroisopropyl iodide in a glass ampoule at 260-290 °C. The molecular structures of the four new compounds have been determined by means of X-ray single crystal diffraction partially also by use of synchrotron radiation. Theoretical calculations at the DFT level of theory have been employed to rationalize the energetics of isomers and of C₆₀-R_f binding.     

Zn(C3H3N2)2: a novel diamagnetic insulator

We have prepared polycrystalline samples of Zn(C₃H₃N₂)₂ by a liquid-mix technique. Characterization of the obtained samples has been performed with the aid of elemental, thermogravimetric, infrared spectra and X-ray powder diffraction analysis. We have measured electric permittivity (ε′, ε″), ac-conductivity (σ_ac), magnetic susceptibility (χ) and specific heat (C_p). The obtained data indicate that this material is a new diamagnetic insulator. A maximum around is found in C_pT⁻³, and it is suggested that in addition to the Debye lattice contribution, there exists a low-frequency mode assigned as an Einstein mode contribution to the total specific heat. As a main result of the study, we found ε′ to be constant in a wide temperature range and to have a small value of 2.3 at room temperature. This feature in combination with other properties like crystallization, good thermal stability (up to 400°C), weak moisture sensitivity and simple synthesis makes Zn(C₃H₃N₂)₂ to be a promising candidate for good insulating material in various applications.     

Gas phase electron diffraction study of basketene,C10H10

A gas phase electron diffraction study of the cage hydrocarbon, basketene, is reported. A least squares treatment of molecular intensities has been carried out in terms of a geometrically consistent r_α structure. The mean amplitude values and shrinkage corrections have been calculated using the force field parameters estimated from the data on simpler molecules.Structure refinement of the C_2v molecular model yields the following parameter values (bond lengths, r_a, in nm; angles, r_α in degrees): <C₂—C_3, C₄—C₅?_av 0.1609(14); C₃—C₄ 0.1563(6); C₉C₁₀ 0.1360(9); C₁—C₁₀ 0.1511(13); C₁—C₂ 0.1517(9); <C-H>_av. 0.1092(8); <C₃C₄C₇ 88.5(1.0); dihedral angle C₃C₄C₇/C₃C₅C₇ 153.8(1.0). Parenthesized are three times the standard deviation values, 3σ.In addition to the geometric parameters listed, the mean amplitudes for all bonded and C· C nonbonded distances have been determined by the least squares method. All the other amplitudes (C· H and H· H) have been fixed at the values estimated from the spectral data.Comparison of the results obtained with the literature data on similar polycyclic molecules points to the stronger internal strain in the basketene molecule.     

Solvothermal synthesis of an open-framework zinc chlorophosphate, [C8N4H26][Zn3Cl(HPO4)3(PO4)], with a layer structure

A solvothermal reaction of ZnO, HCl, H₃PO₄, and N,N′(3-bisaminopropyl)-1,2-ethylenediamine (BAPEN) in diethyleneglycol at 160°C yields a new zinc chlorophosphate, [C₈N₄H₂₆][Zn₃Cl(HPO₄)₃(PO₄)], I. The structure comprises ZnO₄, ZnO₃Cl, HPO₄ and PO₄ tetrahedral units connected through their vertices giving rise to a layered structure with 10-membered apertures. The position of the Zn and P atoms gives rise to double-four ring like building unit with one Zn missing. The fully protonated amine molecules occupy the inter-lamellar region and interacts with the framework through N-H?O hydrogen bonds. Crystal data: M=792.85, orthorhombic, space group=Pca2₁ (no. 29), a=9.8410(2), b=15.0912(2), c=16.1220(4) Å, V=2394.32(8) Å³, Z=4, ρ_calc=2.199 g cm⁻³, μ(MoKα)=3.443 mm⁻¹, R₁=0.0520, wR₂=0.1256 and S=1.054.     

A novel layered bimetallic phosphite intercalating with organic amines: Synthesis and characterization of Co(H2O)4Zn4(HPO3)6·C2N2H10

A new layered cobalt-zinc phosphite, Co(H₂O)₄Zn₄(HPO₃)₆·C₂N₂H₁₀ has been synthesized in the presence of ethylenediamine as the structure-directing agent. The compound crystallizes in the monoclinic system, space group Cc (No. 9), a=18.2090(8), b=9.9264(7), c=15.4080(7) Å, β=114.098(4)°, V=2542.3(2) Å³, Z=4, R=0.0323, wR=0.0846. The structure consists of ZnO₄ tetrahedra, CoO₆ octahedra and HPO₃ pseudopyramids through their vertices forming bimetallic phosphite layers parallel to the ab plane. Organic cations, which reside between the inorganic layers, are mobile and can be exchanged by NH₄⁺ cations without the collapse of the framework.     

The new silver(I)thioantimonate(III) [C4N2H14][Ag3Sb3S7] and a new structural variant of the silver(I)thioantimonate(III) [C2N2H9]2[Ag5Sb3S8] both synthesized under solvothermal conditions

The novel silver(I)thioantimonates(III) [C₄N₂H₁₄][Ag₃Sb₃S₇] (I) (C₄N₂H₁₂=1,4-diaminobutane) and [C₂N₂H₉]₂[Ag₅Sb₃S₈] (II) (C₂N₂H₈=ethylenediamine) were synthesized under solvothermal conditions using AgNO₃, Sb, S and the amines as structure directing molecules. Both compounds crystallize as orange needles with lattice parameters a=6.669(1) Å, b=30.440(3) Å, c=9.154(1) Å for I (space group Pnma), and a=6.2712(4) Å, b=15.901(1) Å, c=23.012(2) Å, β=95.37(1)° for II (space group P2₁/n). In both compounds the primary building units are trigonal SbS₃ pyramids, AgS₃ triangles and AgS₄ tetrahedra. In I the layered [Ag₃Sb₃S₇]²⁻ anion is constructed by two different chains. An [Sb₂S₄] chain running along [100] is formed by vertex sharing of SbS₃ pyramids. The second chain contains a Ag₃SbS₅ group composed of the AgS₄ tetrahedron, two AgS₃ units and one SbS₃ pyramid. The Ag₃SbS₅ units are joined via S atoms to form the second chain which is also directed along [100]. The layered anion is then obtained by condensation of the two individual chains. The organic structure director is sandwiched by the inorganic layers and the shortest inter-layer distance is about 6.4 Å. In II the primary building units are linked into different six-membered rings which form a honeycomb-like layer. Two such layers are connected via Ag-S bonds of the AgS₄ tetrahedra giving the final undulated double layer anion. The structure directing ethylenediamine cations are located in pairs between the layers and a sandwich-like arrangement of alternating anionic layers and organic cations is observed. The inter-layer separation is about 5.4 Å. Both compounds decompose in a more or less complex manner when heated in an argon atmosphere. The optical band gaps of about 1.9 eV for the two compounds proof the semiconducting behavior. For II the conductivity was measured with impedance spectroscopy and amounts to σ_295K=7.6×10⁻⁷ Ω⁻¹ cm⁻¹. At 80 °C the conductivity is significantly larger by one order of magnitude.     

A novel 1D organic-inorganic hybrid based on alternating heteropolyanions [GeMo12O40] and isopolyanions [Mo6O22]

A novel one-dimensional (1D) coordination polymer [{Cu(2,2′-bpy)}₆(Mo₆O₂₂)][GeMo₁₂O₄₀]·H₂O (2,2′-bpy=2,2′-bipyridine), which represents the first example of 1D organic-inorganic hybrid based on a Keggin-type heteropolyanion [GeMo₁₂O₄₀]⁴⁻ and an unprecedented isopolyanion [Mo₆O₂₂]⁸⁻, has been hydrothermally synthesized and characterized by single crystal X-ray diffraction. Crystal data: C₆₀H₅₀Cu₆GeMo₁₈N₁₂O₆₃, monoclinic, P2₁/c, a=13.9344(3), b=20.0329(3), c=17.2151(3) Å; β=94.0220(10)°, V=4793.70(15) Å³, T=293(2) K; Z=2.     

Hydrothermal synthesis and structural characterization of two organically templated zincophosphites with three-dimensional frameworks, (C6H14N2)·[Zn3(HPO3)4] and (C4H12N2)·[Zn3(HPO3)4]

Two organically templated zincophosphites, (C₆H₁₄N₂)·[Zn₃(HPO₃)₄] and (C₄H₁₄N₂)·[Zn₃(HPO₃)₄] have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction. (C₆H₁₄N₂)·[Zn₃(HPO₃)₄] crystallizes in the triclinic space group , with cell parameters, a=9.363(4) Å, b=10.051(4) Å, c=10.051(4) Å, α=85.777(13)°, β=82.091(9)°, and γ=79.783(9)°. (C₄H₁₄N₂)·[Zn₃(HPO₃)₄] crystallizes in the monoclinic space group P2₁/c, with cell parameters, a=9.9512(3) Å, b=10.1508(3) Å, c=17.8105(5) Å, and β=95.6510(10)°. Although the two structures are different, they have the same anionic framework compositions of [Zn₃(HPO₃)₄]²⁻. Their frameworks are built up from strictly alternating ZnO₄ tetrahedra and HPO₃ pseudo pyramids by sharing vertexes. There exist channels with an eight-membered ring window along the a- and c-axis. Powder X-ray diffraction, IR spectroscopy, ³¹P MAS solid-state NMR, thermogravimetric and differential thermal analyses were also carried out.     

Gas transport properties of 6FDA-TMPDA/MOCA copolyimides

The gas permeation behavior of 2,2′-bis(3,4′dicarboxyphenyl) hexafluoropropane dianhydride(6FDA)-2,4,6-trimethyl-1,3-phenylenediamine (TMPDA)/4,4′-methylene bis(2-chloroaniline) (MOCA) copolyimides was investigated by systematically varying the diamine ratios. All the copolyimides were soluble in most of the common solvents. The gas permeabilities and diffusion coefficients decreased with increasing MOCA content; however, the permselectivity of gas pairs such as H₂/N₂, O₂/N₂, CO₂/CH₄ was enhanced with the incorporation of MOCA moiety. Moreover, all of the copolyimides studied in this work exhibited performance near, lying on or above the existing upper bound trade-off line between permselectivity and permeability.     

Vapour-liquid equilibrium data for the systems C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2

High pressure vapour-liquid equilibrium data for the C₂H₆ + N₂, C₂H₄ + N₂, C₃H₈ + N₂, and C₃H₆ + N₂ systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured.Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work.     

Synthesis and Structure of a New Layered Zincophosphate Zn6(PO4)5(HPO4)·C8N5H28·5H2O, Intercalated with Quintuply Protonated Tetraethylenepentamine

A new two-dimensional zinc phosphate Zn₆(PO₄)₅(HPO₄)·C₈N₅H₂₈·5H₂O has been synthesized hydrothermally using tetraethylenepentamine (TEPA) as structure-directing agent and its structure was determined by means of single-crystal X-ray diffraction. The title compound crystallizes in the orthorhombic system, space group Pca2₁ (No.29) with lattice parameters a=18.6286(12) Å, b=8.0804(5) Å, c=22.5019(15) Å, V= 3387.1(4) ų, Z=4, R₁=0.0389 and wR₂=0.0862 [4042 observed reflections with I>2σ(I)]. The structure involves a network of ZnO₄, PO₄, and PO₃(OH) tetrahedra forming macroanionic inorganic layers with eight-membered apertures. The charge compensation is achieved by the quintuply protonated TEPA molecule in interlamellar space, which interact with the inorganic layers via hydrogen bonding.